style(lib): remove lints that have been removed in newer clippy (#4167)

The following lints no longer exist in recent clippy versions and cause
`unknown lint` errors (promoted to errors by `-D warnings` / `-W unknown-lints`):

- clippy::unnecessary_rest_pattern
- clippy::rest_pattern_accessible_field
- clippy::definition_in_module_root

Remove them from the allowed lints list in Cargo.toml.

Author: tangaac

Cargo.toml

@@ -139,11 +139,9 @@ panic = "allow"
 pattern_type_mismatch = "allow"
 redundant_closure_for_method_calls = "allow"
 redundant_else = "allow"
-rest_pattern_accessible_field = "allow" # TODO: consider, might catch bugs
 single_char_lifetime_names = "allow"
 struct_excessive_bools = "allow" # TODO: bogus lint?
 trivially_copy_pass_by_ref = "allow"
-unnecessary_rest_pattern = "allow" # TODO: simple fix
 unnecessary_trailing_comma = "allow"
 unnested_or_patterns = "allow"
 unused_async = "allow" # TODO: is it for API?
@@ -160,7 +158,6 @@ clone_on_ref_ptr = "allow" # Arc::clone(blah) is needlessly noisy
 cognitive_complexity = "allow" # is this ever useful?
 decimal_literal_representation = "allow" # arguably more human-readable
 default_numeric_fallback = "allow" # too many false positives
-definition_in_module_root = "allow" # this is normal
 expect_used = "allow" # expect is self-documenting
 error_impl_error = "allow" # mod::Error is a fine name
 field_scoped_visibility_modifiers = "allow" # possibly good idea, noisy for now